This is a new application that concerns the development and optimization of a new generation of photosensitizers for photodynamic therapy (PDT) of tumors and other health conditions. The molecules selected for study are, chemically, of the naphthalocyanine (NC) family. NC's are based on a tetrapyrroloid macrocycle. Preliminary photophysicial studies have shown one representative of this class as having light absorption and photochemical characteristics that are required for improving upon the performance of the photosensitizer (hematoporphyrin derivative) currently undergoing chemical trials. The program involves a synthetic facet in which NC's of different structure, optical absorption and solubility properties will be synthesized and characterized (Dr. M. E. Kenny will collaborate here). There is a facet that requires the use of time- resolved kinetic methods to quantify the photophysical properties of the designated systems in a variety of environments. The third facet involveds photobiological studies at the cellular and animal tumor level (these last in collaboration with Dr. G. Jori). The three laboratories where this research will proceed are all excellently equipped with the requisite facilities.